How many calories are in mushrooms?

Fresh mushrooms are extremely low in calories, containing just 8 kcal per 100g for most common varieties (button, chestnut, shiitake). Whole button mushrooms can be slightly higher at 18 kcal/100g due to lower water content. An 80g serving provides only 6-14 kcal, making mushrooms one of the lowest-calorie foods you can eat.

Are mushrooms a good source of vitamin D?

Mushrooms are one of the only non-animal food sources of vitamin D. When exposed to UV light (either sunlight or commercial UV treatment), mushrooms produce significant amounts of vitamin D2. Tesco sells specific 'Vitamin D' labelled chestnut and portobello mushrooms that have been UV-treated. Regular mushrooms grown in the dark contain very little vitamin D. For plant-based eaters, UV-treated mushrooms are one of the best dietary sources.

What is the difference between button, chestnut, and portobello mushrooms?

Button, chestnut, and portobello mushrooms are all the same species (Agaricus bisporus) at different stages of maturity. Button mushrooms are harvested youngest and have a mild flavour. Chestnut (or cremini) mushrooms are slightly more mature with a firmer texture and deeper flavour. Portobello mushrooms are the fully mature form — large, flat, and meaty. Nutritionally they are virtually identical (all around 8 kcal/100g). Shiitake mushrooms are a different species with a more intense umami flavour but similar nutritional profile.

Glucose: Very LowNOVA 1

Nutritional Information for Mushrooms

Mushrooms are one of the lowest-calorie foods available, providing just 8-18 kcal per 100g depending on the variety. From a SpikeSaver perspective, they are virtually invisible to blood glucose — with only 0.2-0.3g of carbohydrates per 100g, the glycaemic impact is negligible. All fresh mushrooms are NOVA 1 (unprocessed), and they are one of the only non-animal food sources of vitamin D (when exposed to UV light). This page covers button, chestnut, portobello, and shiitake varieties, all available at Tesco.

Nutrition per 100g

Nutrient	Per 100g	Per serving
Energy	8 kcal / 35 kJ	6 kcal
Protein	1g	0.8g
Carbohydrates	0.3g	0.2g
of which sugars	0.3g	—
Fat	0.2g	0.2g
of which saturated	0.1g	—
Fibre	0.7g	—
Salt	0.01g	—

Serving size: 80g (handful, roughly 4-5 button mushrooms) · Source: Tesco product page, October 2025

Glucose impact

Glycemic Index

Very Low

Glucose risk

Mushrooms contain just 0.2-0.3g of carbohydrates per 100g — one of the lowest carbohydrate contents of any food. Even eating 500g of mushrooms would deliver less than 2g of carbs. The glycaemic index is negligible and unmeasurable in practice. Mushrooms are one of the safest foods for anyone managing blood glucose levels.

Processing level

NOVA 1 (unprocessed)

Fresh mushrooms of any variety — button, chestnut, portobello, shiitake — are unprocessed single-ingredient whole foods. The ingredient is simply mushrooms. There are no additives, preservatives, or processing aids. Even pre-sliced and packaged mushrooms remain NOVA 1. The only mushroom products to watch are tinned or dried mushrooms with added salt (NOVA 2-3) or mushroom-based sauces and soups (NOVA 3-4).

Mushrooms at Tesco

Source: Tesco product page, October 2025

Tesco Baby Button Mushrooms 200G

£1.15*NOVA 1 (unprocessed)

Tesco Organic Chestnut Mushrooms 250 G

£2.25*NOVA 1 (unprocessed)

Tesco Family Pack Chestnut Vitamin D Mushrooms 485G

£1.90*NOVA 1 (unprocessed)

Tesco Finest Shiitake Mushrooms 125G

£1.80*NOVA 1 (unprocessed)

Tesco Finest Portobello Vitamin D Mushrooms

£1.30*NOVA 1 (unprocessed)

*Prices were correct at the time of collection and may have since changed. Check Tesco.com for current pricing.

What to watch for when shopping

All fresh mushrooms at Tesco are NOVA 1 — there is nothing to worry about with any variety. The biggest nutritional difference between types is minimal: button, chestnut, portobello, and shiitake all hover around 8 kcal/100g with nearly identical macros. The standout feature is vitamin D: Tesco's 'Vitamin D' labelled mushrooms (chestnut and portobello) have been exposed to UV light, boosting their vitamin D content significantly. Mushrooms are also a good source of B vitamins (riboflavin, niacin, pantothenic acid) and contain selenium and potassium. Budget tip: Tesco Baby Button Mushrooms 200G at £1.15 (£5.75/kg) offer the best value, while the Family Pack Chestnut at £1.90 for 485g (£3.92/kg) is cheapest per kilo.

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